The manager of the customer service department of Data Tech Credit Card Service Company is concerned about the number of defects produced by the billing process. Every day a random sample of 250 statements was inspected for errors regarding incorrect entries involving account numbers, transactions on the customer's account, interest charges, and penalty charges. Any statement with one or more of these errors was considered a defect. The study lasted 30 days and yielded the data in Table 3.5.

a. Construct a p-chart for the billing process.

b. Is there any nonrandom behavior in the billing process that would require management attention?

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TABLE 3.5 SAMPLE DATA FOR DATA TECH CREDIT CARD SERVICE Number of Errors in Sample of 250 Sampies 1-10 11-20 21-30 12 13 12 10 10